NestedDelegatingExpressionAggregationOperationContext.java

/*
 * Copyright 2016-present the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.springframework.data.mongodb.core.aggregation;

import java.util.Collection;

import org.bson.Document;

import org.bson.codecs.configuration.CodecRegistry;
import org.jspecify.annotations.Nullable;
import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExpressionFieldReference;
import org.springframework.data.mongodb.core.aggregation.ExposedFields.FieldReference;
import org.springframework.util.Assert;

/**
 * {@link AggregationOperationContext} that delegates {@link FieldReference} resolution and mapping to a parent one, but
 * assures {@link FieldReference} get converted into {@link ExpressionFieldReference} using {@code $$} to ref an inner
 * variable.
 *
 * @author Christoph Strobl
 * @author Mark Paluch
 * @since 1.10
 */
class NestedDelegatingExpressionAggregationOperationContext implements AggregationOperationContext {

	private final AggregationOperationContext delegate;
	private final Collection<Field> inners;

	/**
	 * Creates new {@link NestedDelegatingExpressionAggregationOperationContext}.
	 *
	 * @param referenceContext must not be {@literal null}.
	 */
	NestedDelegatingExpressionAggregationOperationContext(AggregationOperationContext referenceContext,
			Collection<Field> inners) {

		Assert.notNull(referenceContext, "Reference context must not be null");
		this.delegate = referenceContext;
		this.inners = inners;
	}

	@Override
	public Document getMappedObject(Document document) {
		return delegate.getMappedObject(document);
	}

	@Override
	public Document getMappedObject(Document document, @Nullable Class<?> type) {
		return delegate.getMappedObject(document, type);
	}

	@Override
	public FieldReference getReference(Field field) {

		FieldReference reference = delegate.getReference(field);
		return isInnerVariableReference(field) ? new ExpressionFieldReference(delegate.getReference(field)) : reference;
	}

	private boolean isInnerVariableReference(Field field) {

		if (inners.isEmpty()) {
			return false;
		}

		for (Field inner : inners) {
			if (inner.getName().equals(field.getName())
					|| (field.getTarget().contains(".") && field.getTarget().startsWith(inner.getName()))) {
				return true;
			}
		}

		return false;
	}

	@Override
	public FieldReference getReference(String name) {
		return new ExpressionFieldReference(delegate.getReference(name));
	}

	@Override
	public Fields getFields(Class<?> type) {
		return delegate.getFields(type);
	}

	@Override
	public CodecRegistry getCodecRegistry() {
		return delegate.getCodecRegistry();
	}
}